Haemoglobin (Haeme=iron; globin=a type of protein) is the main component of red blood cells (RBCs). It is a protein that carries oxygen from the lungs to the rest of the body, and carries carbon dioxide from the rest of the body to the lungs. The haemoglobin level is usually measured, along with other investigations, as part of the complete blood count (CBC).
Why is the test done?
The level of haemoglobin is measured to check the oxygen carrying capacity of the blood. The low oxygen carrying capacity of the blood leads to the symptoms of anaemia (low level of haemoglobin).
How is it done?
Blood is drawn from a vein, usually from the inside of the elbow. The puncture site is cleaned with an antiseptic, and an elastic band is put around the upper arm to apply pressure. This causes veins below the band to fill with blood. A needle is put into the vein, and the blood is collected into an airtight vial or a syringe. After the blood has been collected, the needle is removed, and the puncture site is pressed to stop any bleeding. No special preparation is required for the test.
If only haemoglobin is to be tested, the blood can be obtained from a finger prick. The total amount of haemoglobin in the blood is measured by a simple test in the laboratory.
What are the risks?
Multiple punctures may be required to locate the veins
Blood may collect under the skin
There is a very small risk of infection or continued bleeding from the puncture site if pressure is not applied long enough.
What are the normal values?
Males: 13 to 17 gm/dl (grams per decilitre)
Females: 12 to 16 gm/dl
What are the abnormal results?
Less than normal levels are seen in various types of anaemia (low haemoglobin concentration):
Malnutrition and nutritional deficiencies of iron, folate, vitamin B12, vitamin B6
Red blood cell destruction due to a transfusion reaction
Excessive intake of fluids (over hydration – temporary dilution of haemoglobin level)
More than normal levels may be seen in:
Congenital heart disease
Lung diseases like cor pulmonale and lung fibrosis
Polycythemia vera or increased RBC formation due to excess of erythropoietin.